“We have the primary tumor, the original cancer. We often mostly don't have samples of the actual cancer once it comes back in an aggressive form,” Carey said. “To scientifically understand the actual cancer after it occurs is much more important than how it started.”

“That gives us some idea of when we give treatment and cancers become resistant, how they do it,” she added.

Carey says cancers often look different in the lungs, the liver or the brain.

“What are the shared features that cause it to be able to metastasize?” she said.

Those answers will come from women who are in end-of-life care, like Williams, who still want to fire a parting shot at breast cancer.

“I just want to do good, you know? I just feel it's the reason I'm going through it right now,” she said.﻿